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UVC To Remove Suspended Algae In Pond Water. Beware Green Algae Blooms

We must unfortunately accept that even in the best fish ponds algae will always be a threat. By far the best way to control suspended algae, and it works every time for this type of algae, is to install a CORRECTLY SIZED UV light before the filter (or these days more often than not the UVC is part of the pond filter). This works very simple, water containing the suspended algae is pumped through the Ultra Violet (UVC) light device and all the algae (and only those pumped through the light) are killed by exposure to UV light.

Upon dying dead algae clump together becoming much bigger than 4 microns. Because they are now much bigger this means most well designed filters are able to remove the dead algae. In all likelihood the algae are still forming in your pond but the UV light is killing them FASTER than they are forming.

It is important to remove the dead algae in a filter because if they are allowed to sink to the bottom of the pond they can pollute the water quite badly and remove oxygen from the pond water.

When a pond is badly infected by green water then your fish can all suddenly die and this happens overnight normally. The reason is again simple and is because algae are plants - they produce oxygen during the day (in the photosynthesis process) but they produce carbon dioxide at night by taking oxygen out of the water.

Algae in large mass can totally deplete the oxygen from a pond. The fish will therefore suffocate. This is also very much more common in heat wave situations because at higher temperatures water can hold less oxygen anyway.

Algaecides can be effective in ponds but have to be used continuously and very carefully. They are not recommended for green water ponds when you can get yourself an UV clarifier. The UVC (ultra violet light clarifier) is one of the very best inventions in pond keeping.

The Danger Of Algae Blooms

The section that follows is important not just as far as algae blooms are concerned but also for a general understanding of what happens within any pond.

Think of your pond as breathing in oxygen during the day and breathing out carbon dioxide at night. Carbon dioxide in pond water results from a number of sources including:

  • Waste products decaying at the bottom of the pond

  • Respiration by pond inhabitants.... fish, insects, plants, algae

Of course all of us think first and foremost of oxygen in pond water as being essential and of course this is very true. Carbon dioxide is also of critical importance. Oxygen and carbon dioxide also work in concert with each other. In simple terms as carbon dioxide levels increase in a pond then oxygen levels tend to decrease. This follows a natural diurnal and nocturnal pattern in planted ponds. From dawn to dusk (ie daytime) oxygen levels in a planted pond increase then decrease once evening sets in. Carbon dioxide concentrations act in reverse fashion. They fall during the daytime and increase throughout the night. Oxygen levels are at their highest at dusk and carbon dioxide levels are at their highest at dawn.

Beware algae blooms in ponds

Let's equate the above to what living organisms do in the pond. Think of the flora and fauna as exhaling carbon dioxide while inhaling oxygen during the night.

From this you will agree that dawn is the critical time in a pond. Often people wake up to find dead fish and wondered what happened. Such deaths could be associated with very low oxygen levels coinciding with high carbon dioxide levels. When ponds are full of suspended algae such problems can arise.

If there is a very small amount of algae bloom in the pond then you will find oxygen and carbon dioxide levels will not change significantly between early morning and late afternoon. On the other hand dense pea soup type water will show very significant variations.

If you want to understand the whole process of pond filtration then go through these articles in the order presented.


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